The Sun is by far the most studied star. The solar structure, revealed by helioseismology and solar neutrinos, is well determined, and accurate solar models give information about the past, present and the future of the Sun. These solar models, or Standard Solar Models (SSM), are useful for describing the solar interior, and at the same time provide a deeper knowledge on other disciplines, such as stellar structure and evolution, particle physics and even non-standard physics. In fact, the extreme conditions of the solar interior allow studying physics in environments that are hard to reproduce in earth-based experiments. Consequently, the Sun is a powerful laboratory to test non-standard particle physics. In particular, the Sun offers very interesting possibilities for studying weakly interacting light particles that arise from extensions of the Standard Model of particles to address some of the open questions in fundamental physics, such as the nature of dark matter.
The main goal of this thesis is to use solar models to study the impact of different types of weakly interacting particles on the solar structure. Then, based on the structural changes they produce, the goal is to set the most restrictive bounds to properties of these particles using solar data from helioseismology and neutrinos.
In order to pursue this goal, it is important to have realistic solar models that reproduce the available observations. Motivated by this fact, this thesis presents a new generation of SSMs that includes recent updates on some important nuclear reaction rates and a consistent treatment of the equation of state. Models also include updated errors computed using Monte-Carlo simulations and a novel and flexible treatment of opacity uncertainties based on opacity kernels, required in the light of recent theoretical and experimental works on radiative opacity. In fact, radiative opacities are proposed as one of the possible solutions to the \emph{solar abundance problem}, that is the conflict between helioseismic predictions from the models and observations when new releases of the solar composition are used to construct the SSM, in contrast to the good agreement obtained with the older compositions based on more simplistic model atmospheres. Therefore, it is important to have a good understanding of the current status of the radiative opacities and the corresponding uncertainties.
Current uncertainties in the solar composition and opacities can be overcome for studies of particle physics that do not depend on a detailed knowledge of the solar interior composition. For this purpose, the Best Fit Model, a solar model that better reproduces the observations using realistic evolutionary inputs, is introduced.
Finally, a new statistical analysis that combines helioseismology and solar neutrino observations is presented, and it is used to place upper limits to the properties of non standard weakly interacting particles, and in particular, to axions, hidden photons and minicharged particles. For the fist time, constraints on the properties of these particles are placed by using a method that combines both helioseismology and solar neutrino observations. Additionally, the fact that Best Fit Models are the basis of the statistical analysis results in more robust bounds independent on the \emph{solar abundance problem}. The bounds obtained are: for the axion-photon coupling constant $g_{10} < 4.1$ at 3 C.L., for the product of the kinetic mixing and mass of hidden photons, $\chi m < 1.8 \cdot 10^{-12}~\rm{eV}$ at 3 C.L and for the change of the minicharged particles, $\epsilon=2.2 \cdot 10^{-14}$ at 2 CL for $m_f = 0 - 25~\rm{eV}$. The results are the most restrictive solar bounds, being aproximately a factor 2 better than previous ones. Moreover, the results obtained for hidden photons and minicharged particles are globally the most restrictive bounds.